import java.util.Scanner;

/**
 * Created by dllo on 18/3/30.
 */
public class Question01 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入一个数:");
        int sum = 0;
        int n = scanner.nextInt();
        for (int i = 1; i <= n; i++) {
            sum += i;
        }
        System.out.println("和是:" + sum);
    }
}
